Across
- 2. a cloud of gas and dust in outer space
- 3. the natural satellite of Earth
- 5. a fixed luminous point in the sky, remote incandescent body like the Sun
- 7. the rapid expansion of matter
- 8. a hypothetical space object about the size of Mars that many astronomers believe once existed in the solar system, following an orbit similar to that of Earth and that collided with Earth
- 9. the force that attracts a body towards objects with mass
Down
- 1. a celestial body moving in an elliptical orbit round a star
- 4. the curved path of an object round a star, planet or moon
- 6. a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction